The present invention relates to a light-sensitive composition which can be effectively used for making lithographic printing plates, IC circuits and photomasks and more specifically to a negative working light-sensitive composition which comprises a polymeric compound highly soluble in an aqueous alkaline developer.
There have been well known photocross-linkable materials capable of cross-linking through a cyclization-addition reaction and these compounds have widely been used as a principal component of a light-sensitive composition for use in making lithographic printing plates or the like. As such photocross-linkable polymeric compounds, useful are those having maleimido groups on the side chains and those having cinnamyl, cinnamylidene and/or chalcone groups, which have photodimerizable unsaturated double bonds adjacent aromatic nuclei, on the side chains or in the main chain.
Negative working presensitized plates for use in making lithographic printing plates (hereunder referred to as "negative working PS plates") or the like are roughly divided into two groups, one of which is alkali-developable type one whose un-exposed portions are removed by (or developed with) an aqueous alkali developer and the other of which is solvent-developable type one whose un-exposed portions are removed by (or developed with) an organic solvent type developer. From the viewpoint of safety and hygiene in work operations, the alkali-developable PS plates are favorable. Whether a PS plate is alkali-developable or solvent-developable is mainly determined depending on the properties of the photocross-linkable polymeric compound used.
There have been known various methods for making a photocross-linkable polymeric compound alkali-soluble. For instance, Japanese Patent Un-examined Publication (hereunder referred to as "J.P. KOKAI") No. Sho 52-988 (U.S. Pat. No. 4,079,041) and Japanese Patent Publication for Opposition Purpose (hereunder referred to as "J.P. KOKOKU") No. Sho 49-28122 (U.S. Pat. No. 4,297,470) disclose methods which comprise copolymerizing a low molecular weight compound having a photocross-linkable group and a polymerizable unsaturated bond with methacrylic acid or acrylic acid to form such an alkali-soluble polymeric compound; J.P. KOKOKU No. Sho 57-56485 discloses a method which comprises copolymerizing a low molecular weight compound having a photocross-linkable group and a polymerizable unsaturated bond with maleic acid anhydride and then hydrolyzing the resulting copolymer; J.P. KOKAI No. Sho 59-218440 discloses a method which comprises forming carboxylic groups on a polymeric compound comprising carboxylic acid anhydride units while introducing photocross-linkable groups therein through a polymer reaction; J.P. KOKAI No. Sho 48-74594 discloses a method comprising introducing photocross-linkable groups into a polyacrylic acid through a polymer reaction; J.P. KOKAI No. Sho 60-191244 (U.S. Pat. No. 4,640,887) discloses a method which comprises reacting a polyester prepolymer having photodimerizable unsaturated double bonds adjacent to aromatic nuclei in the main chain, carboxyl groups on the side chains and hydroxyl groups on the termini with a chain-lengthening agent having at least two functional groups capable of reacting with hydroxyl groups such as diisocyanate compounds, diphenyl terephthalate, diphenyl carbonate or terephthaloylbis(N-caprolactam); and further there have been proposed a method of comprising reacting a polyester prepolymer or an urethane prepolymer having photodimerizable unsaturated double bonds adjacent to aromatic nuclei in the main chain and hydroxyl groups on the termini with a chain-lengthening agent such as pyromellitic dianhydride or cyclopentanetetracarboxylic acid dianhydride to introduce carboxyl groups in the side chains.
On the other hand, as aqueous alkaline developer compositions which are used to develop exposed negative working PS plates, there may be mentioned, for instance, those comprising benzyl alcohol, an anionic surfactant, an alkaline agent and water as disclosed in J.P. KOKAI No. Sho 51-77401; those consisting of an aqueous solution containing benzyl alcohol, an anionic surfactant and a water-soluble sulfite as disclosed in J.P. KOKAI No. Sho 53-44202 (U.S. Pat. No. 4,186,006); and those comprising an organic solvent of which solubility in water is not more than 10% by weight at ordinary temperature, an alkaline agent and water as disclosed in J.P. KOKAI No. Sho 55-155355.
All of these conventional developer compositions comprise organic compounds such as organic solvents and/or surfactants. However, organic solvents suffer from various drawbacks, for instance, these organic compounds being in general toxic, giving out bad smell, possibly becoming a cause of a fire, the waste liquor thereof being greatly inhibited by the BOD regulation and too much expences being required. On the other hand, the surfactants cause foaming during development operations. For this reason, it is desirable that developer compositions substantially free of these organic substances be employed.
Under such circumstances, there have been proposed a variety of developer compositions substantially free of organic substances such as those disclosed in J.P. KOKAI No. Sho 59-84241 (U.S. Pat. No. 4,500,625). These developer compositions are intended to be used for developing positive working PS plates which comprise an o-naphthoquinonediazide compound as a light-sensitive compound and they cannot develop negative working PS plates satisfactory (i.e., even after development, part of layers to be removed remains unremoved). In other words, they do not show acceptable developability. Moreover, even if they exhibit apparently acceptable ability to develop negative working PS plates, the resulting lithographic printing plate causes contamination of non-image areas thereof (i.e., background contamination) during printing.
The term "substantially free of organic substances" herein used means that the developer composition comprises not more than 3% by weight and preferably not more than 1% by weight of such organic substances.